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###### Department of Health and Human Services

# AGENCY:

National Institute of Environmental Health Sciences; National Institutes of Health, HHS.

# ACTION:

Request for comment.

# SUMMARY:

                        CERHR announces availability of the hydroxyurea expert panel report by March 5, 2007 on the CERHR Web site (                        *http://cerhr.niehs.nih.gov*) or in print from CERHR (see “                        **ADDRESSES**                        ” below). This expert panel report is an evaluation of the reproductive and developmental toxicity of hydroxyurea conducted by a 13-member expert panel composed of scientists from the Federal Government, universities, and private organizations. CERHR invites the submission of public comments on this expert panel report.                    

# DATES:

The final hydroxyurea expert panel report will be available by March 5, 2007, and written public comments on this report should be received by April 18, 2007.

# ADDRESSES:

                        Public comments and any other correspondence should be sent to Dr. Michael D. Shelby, CERHR Director, NIEHS, P.O. Box 12233, MD EC-32, Research Triangle Park, NC 27709 (mail), (919) 316-4511 (fax), or                         *shelby@niehs.nih.gov*                         (e-mail). Courier address: CERHR, 79 T.W. Alexander Drive, Building 4401, Room 103, Research Triangle Park, NC 27709.                    

# SUPPLEMENTARY INFORMATION:

## Background

                    Hydroxyurea is used in the treatment of cancer, sickle cell disease, and thalassemia. It is the only treatment for sickle cell disease used in children aside from blood transfusion. Hydroxyurea may be used in the treatment of children and adults with sickle cell disease for an extended period of time or for repeated cycles of therapy. Treatment with hydroxyurea may be associated with cytotoxic and myelosuppressive effects and hydroxyurea is mutagenic. Hydroxyurea is FDA-approved for reducing the frequency of painful crises and the need for blood transfusions in adults with sickle cell anemia who experience recurrent moderate to severe crises. CERHR selected hydroxyurea for expert panel evaluation because of (1) increasing use in the treatment of sickle cell disease in children and adults, (2)                           ( print page 8385)                        knowledge that it inhibits DNA synthesis and is cytotoxic, and (3) published evidence of reproductive and developmental toxicity in rodents.                

                    The CERHR convened an expert panel on January 24-26, 2007, to review and revise the draft expert panel report and reach conclusions regarding whether exposure to hydroxyurea is a hazard to human development or reproduction. The expert panel also identified data gaps and research needs. Prior to the meeting, CERHR solicited public comment on the draft expert panel report (                    **Federal Register**                     Vol. 71, No. 199 pp. 60746-60748).                

Following receipt of public comments on the hydroxyurea expert panel report, CERHR staff will prepare the NTP-CERHR monograph. NTP-CERHR monographs are divided into four major sections: (1) The NTP Brief which provides the NTP's interpretation of the potential for the chemical to cause adverse reproductive and/or developmental effects in exposed humans, (2) a roster of expert panel members, (3) the final expert panel report, and (4) public comments received on that report. The NTP Brief is based on the expert panel report, public comments on that report, public and peer review comments on the draft NTP Brief, and any new information that became available after the expert panel meeting.

## Request for Comments

CERHR invites written public comments on the hydroxyurea expert panel report. Written comments should be sent to Dr. Michael Shelby at the address provided above. Persons submitting written comments are asked to include their name and contact information (affiliation, mailing address, telephone and facsimile numbers, e-mail, and sponsoring organization, if any). All comments received will be posted on the CERHR website and will be included in the NTP-CERHR monograph on hydroxyurea. The NTP will consider all public comments during preparation of the NTP Brief.

## Background Information on CERHR

                    The NTP established CERHR in June 1998 [                    **Federal Register**                    , December 14, 1998 (Vol. 63, No. 239, pp. 68782)]. CERHR is a publicly accessible resource for information about adverse reproductive and/or developmental health effects associated with exposure to environmental and/or occupational exposures. Expert panels conduct scientific evaluations of agents selected by CERHR in public forums.                

                    CERHR invites the nomination of agents for review or scientists for its expert registry. Information about CERHR and the nomination process can be obtained from its Web site (                    *http://cerhr.niehs.nih.gov*) or by contacting Dr. Shelby (see                     **ADDRESSES**                     above). CERHR selects chemicals for evaluation based upon several factors including production volume, potential for human exposure from use and occurrence in the environment, extent of public concern, and extent of data from reproductive and developmental toxicity studies.                

                    CERHR follows a formal, multi-step process for review and evaluation of selected chemicals. The formal evaluation process was published in the                     **Federal Register**                     notice July 16, 2001 (Vol. 66, No. 136, pp 37047-37048) and is available on the CERHR Web site under “About CERHR” or in printed copy from CERHR.                

Dated: February 12, 2007.

Samuel H. Wilson,

Deputy Director, National Institute of Environmental Health Sciences and National Toxicology Program.

 [FR Doc. E7-3151 Filed 2-23-07; 8:45 am]

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